Method and apparatus for drying and sterilizing fabrics and the like

ABSTRACT

A method for rapid drying and sterilizing of clothes, fabrics, garments, textiles and the like in which electromagnetic waves (100 to 300,000 MHz.) are combined with a fast moving air stream while the irradiated material rotates slowly in the processing area in a direction transverse to the air stream and the propagated electromagnetic waves. The apparatus of the invention is the size of a conventional home dryer, is noiseless and can dry a 7-pound fabric workload in two to five minutes while destroying all household germs or microbiological contaminants. It is equipped for automatic operation for different kinds of fabrics and health hazards have been eliminated through the use of automatic safety devices.

Sept 20, 1971 R. M. a. BOUCHER 3,605,272 IETHOD AND APPARATUS FOR DRYINGAND STERILIZING FABRICS AND THE LIKE Filod Jun} 28; 1969 3 Sheets-Shut lI 'E l l 5 3 28 3 L /u m L r! 4 Ill-AW 2 n V id 3 4W 2 III 44 Q a X I nv M 3 L 2 Q +1.4: 8 4

INVENTOR.

RAYMOND MAmEL GUT aoucrza W ATTORNEYS 5911b 1971 R. M. G. BOUCHER3,605,272 IETHOD AND APPARATUS FOR DRYING AND STERILIZING FABRICS ANDTHE LIKE Filed .iu1y 2a, 1969 :s Sheets-Sheet a gZS 27 38-? q 477 -36 IQ :1 m I I l l 4- Y I l I l l I I I l l l l I L T: 1 I v INVENTOR.

q RAYMOND MARCEL GUT BOUCt-ER ATTORNEYS 20 1971 I A a. M. s. BOUCI-IER3.605. 72 IB'HIO D AND APPARATUS I'OR DRYING AND S'IBRILIZING FABRICSAND I!!! LIKE 3 Shanta-Shoot 3 INVENTOR. RAYMD MAKEL GUT BOUG'ERATTOHEYS United States Patent 3,605,272 METHOD AND APPARATUS FOR DRYINGAND STERILIZING FABRICS AND THE LIKE Raymond Marcel Gut Boucher,Metuchen, N.J., assignor to Wave Energy Systems, Inc., New York, N.Y.Filed July 28, 1969, Ser. No. 845,329 Int. Cl. B01k 5/00 US. Cl. 34-1 16Claims ABSTRACT OF THE DISCLOSURE A method for rapid drying andsterilizing of clothes, fabrics, garments, textiles and the like inwhich electromagnetic waves (100 to 300,000 MHz.) are combined with afast moving air stream while the irradiated material rotates slowly inthe processing area in a direction transverse to the air stream and thepropagated electromagnetic waves. The apparatus of the invention is thesize of a conventional home dryer, is noiseless and can dry a 7-p0undfabric workload in two to five minutes while destroying all householdgerms or microbiological contaminants. It is equipped for automaticoperation for different kinds of fabrics and health hazards have beeneliminated through the use of automatic safety devices.

This invention relates to a method and apparatus for drying andsterilizing clothes, fabrics, textiles and the like by combiningmicrowave energy with a fast moving gas stream. For a long time attemptshave been made to use microwave energy for drying of clothes, linen,etc. in the home.

It was suggested for instance (US. Pat. No. 3,410,116) that a drumfilled with wet fabrics and made of a material transparent to microwavescould be rotated along its horizontal axis while being irradiated by anexternal stationary microwave source. That patent describes apparatus inwhich a relatively cool airflow, in a direction perpendicular to theaxis of rotation, was used to carry away the moisture desorbed from theirradiated material. In other methods it was suggested that wet fabricsor textiles could be placed inside a microwave oven of the cavity typethrough which cold air would be injected sideways during part or all ofthe irradiation cycle.

The disadvantages of these techniques are obvious to anyone familiarwith the state of the art in microwave processing technology. Forinstance, most of the materials which are usable for microwave energytransmission (glass-ceramic composition such as Pyroceram) are eithertoo expensive to be used as a material for a clothes dryer drum or notsuitable from the viewpoint of mechanical strength (e.g. a fast rotatingpolypropylene drum). In the case of standard ovens into which fabricsare placed in a static position it was quickly discovered thatrelatively large amounts of air had to be used in order to remove thewater vapor uniformly. Therefore, air channeling was always a problemand it was difficult, if not impossible, to meet the requirements forboth uniform air penetration throughout the wet fabrics and the ovensize which is a function of the microwave radiator output.

It is an object of this invention to provide a method which eliminatesthe disadvantages of the old approaches by a proper combination of themicrowave field, with both the air stream and the motion of theirradiated fabrics.

It is also an object of the present invention to provide a clothesdryer-sterilizer which produces satisfactory, economical results througha new design of the irradiation chamber in which most of theelectromagnetic waves are reflected and rereflected so as to concentratethem in the processing area by means of the proper positioning ofreflectors both downstream from the radiator and downstream from themicrowave main beam.

3,605,272 Patented Sept. 20, 1971 "ice It is also an object of thepresent invention to provide both a method and an apparatus whichproduce fast and thorough drying when both the main microwave energybeam from the radiator and the airstream flow are oriented in the samedirection, namely, parallel to the axis of revolution of the fabriccontainer.

It is a further object of this invention to provide a clothesdryer-sterilizer which is less noisy than the prior art machines sincethe rotational speed of the basket or perforated drum which contains theirradiated material has been reduced down to a level of one to tenrevolutions per minute.

It is .a further object of this invention to provide an economicalmicrowave system for the drying-sterilizing of clothes which can beoperated either with continuous or pulsed wave emissions. Satisfactoryresults can be obtained in some cases with an average output from theradiator as low as ten watts.

It is a further object of this invention to provide an apparatus whichwill not only dry clothes or fabrics in a far shorter time than half theusual drying time of con ventional dryers but will also provide completesterilization in a matter of minutes through the total destruction ofmicroorganisms, bacteria, viruses or even hard to die spores such asBacillus subtilus var. nigr.

It is a further object of this invention to provide a fully automated,clothes dryer-sterilizer which is push-button operated and allows safedrying of a wide variety of fabrics (wool, silk, synthetic fibers, etc.)while having the same overall dimensions and flexibility of todays fixedor movable home clothes dryers.

Other objects, advantages, features and uses will be apparent during thecourse of the following discussion. To aid in the understanding of thepresent invention, we shall briefly discuss the parts played bymicrowave energy, internal heat, and air turbulence during thedrying-sterilizing process.

As is well known, microwave energy is coherent electromagnetic energy.By this we mean that it is ordered. In other words, we can readilyidentify its characteristics and can control it with precision. Thermalenergy, on the other hand, has random, disordered, characteristics whichare not so easily controlled. Although the term microwave, in general,covers a rather wide range of frequencies (from MHz. up to severalhundred thousands MHz.), the present invention mainly contemplates theuse of frequencies between 100 and 23,000 MHz.

The mechanism through which microwave heating occurs at thesefrequencies is based upon the dipole moment, or polarization of themolecules of the irradiated substance. When the polar molecules(absorbed water in the case of the present invention) are subjected to astrong alternating field, their rapid reorientations within the fieldcreate some kind of internal friction resulting in heat. In a moreprecise sense, one could say that heat is produced through theconversion of the potential energy of polarization into random energy.It is important to note that with microwave heating, no contact with thesubstance itself is required. In other words, the transfer of energytakes place directly without the necessity of an intermediate mediumsuch as a hot surface or a high temperature air stream. Energy transferoccurs Wherever the field penetrates. By a proper choice of thematerials used in the construction of our dryer-sterilizer it is thenpossible to produce heat exclusively inside the wet fabrics whilekeeping the walls and all the mechanical components of the processingchamber (rotating basket, supports, etc.) cool.

The advantages of this approach over conventional, hot air, dryers basedon heat conduction phenomena are numerous. Microwave heating eliminatesthe inherent inefficiency of generating thermal energy at an outsidesource. It also eliminates the inefliciency of transferring heat from anexternal source to the fabric load and reduces eventual reradiationlosses. Since microwave energy can be switched on to full power levelsand off again by simply flipping a switch, the time lags associated withthermal processes are not present either. It should also be noted thatin water removal, less power is absorbed by the fabrics as dryingprogresses, so that overheating, which often damages delicate fabrics,cannot occur.

Although the advantages set forth above were known to those skilled inthe art, no home type clothes dryer has been successfully developed inthe past. This is mainly due to the fact that very little attention hasbeen paid to the requirements for removal of water vapor from thesurface'of fabrics. As is well known (Daltons law), the state ofturbulence in the gas phase above the wet material is an importantfactor which governs the rate of evaporation. In previous designs, arelatively low velocity air flow carried out the moisture veryinefliciently as the bulk of the wet fabrics rotated at relatively highspeed (E500 r.p.m.).

In this invention this deficiency is corrected by forcing a relativelyhigh speed, air stream, having a velocity of the order of between 100and 500 feet per minute, through the bulk of the fabrics which arerotated very slowly. To achieve maximum contact between the incoming airand the irradiated fabrics, both reflected radiated Waves and the airflow follow the same path in the same upwards direction. This allows auniform penetration of the air throughout the bulk of the fabrics whichrotateat a speed low enough to prevent channeling effects. Thecombination of a high power microwave beam with a fast air flow movingin the same direction while the fabrics rotate at the speed of the orderof ten revolutions per minute is one of the key elements of theinvention.

The second major improvement resides in the concentrating of theelectromagnetic waves by means of two reflectors placed at each end ofthe processing area. With such .an arrangement, advantage is taken ofstanding wave effects, reinforcement of the field intensity, anddecrease of the risks of radiation leaks. Moreover, a more eflicient useof the energy radiated from the radiator is made.

As is well known, the amount of power that can be delivered to a cubiccentimeter (or any unit of volume) of wet irradiated fabrics isproportional to the product a tan (SfE where e is the permittivity (theamount of electric field that is produced by the molecules for a givenapplied field), tan 6 is the loss tangent of the material (proportionalto the conductivity), is the frequency and E is the electrical fieldstrength. Since the product 6 tan will vary for each fabric, differentirradiation times (present through a timing device) will be used inorder to dry all fabrics with a fixed output power at a fixed frequency.

The invention contemplates the use of a continuous wave emission or apulsed wave emission. In the latter case, the average power requirementswill be decreased while the lethal effects on microorganisms will beenhanced'due to sharp variations in the electric field gradient (A. P.Wehner, Int. Journ. Biometer, vol. 7, No. 3, 277- 282, 1964). Energysavings with pulsed emissions can be quite significant since onemicrosecond pulses at a repetition rate of 1000 per second deliver apeak power of 250 kw. which corresponds to an average power of only 250watts.

A third important feature of the invention lies in the fact that throughfield concentration effects and rapid changes of field strength one can,besides the thermal phenomena, produce important modifications in themetabolism of microorganisms and spores. The combined result oflocalised dehydration plus electrical field effects is a rapiddestruction of the household germs, bacteria or viruses which are oftenpresent at the end of a laundry,

4 drying operation with conventional hot air dryers. The lethal effectsof electromagnetic waves, distinct from thermal destruction, havealready been reported for yeast at relatively low temperature (K. Robe,Food Process Market, 84-86, March 1966).

In the accompanying drawings, forming a part of this application, and inwhich like numerals are employed to designate like parts throughout thesame:

FIG. 1 is a simplified, elevational view of a preferred form ofapparatus of the invention, with a side wall removed, with theinsulation and electrical connections excluded for simplicity;

FIG. 2 is a sectional view of the apparatus of FIG. 1, taken along thelines 2-2 of FIG. 1, viewed in the direction of the arrows, rotated FIG.3 is a sectional view of the apparatus of FIG. 1 taken along the lines33 viewed in the direction of the arrows, rotated 90";

FIG. 4 is a perspective view of the apparatus of FIG. I seen from thefront (right side of FIG. 1) with the lid closed; and

FIG. 5 is a perspective view of the top of the apparatus of FIG. 4 withthe lid open.

As can be seen from FIG. 1, the apparatus consists of a metal housing Iquite similar to those used today in automatic clothes dryers. Locatedwithin the housing is a basket or drum 2 which is mounted so that itrotates around its vertical axis of revolution x-x. This basket is madeof two concentric, vertical cylinders Whose axial, inner section iscovered at the top 3 and the bottom 4 by two welded metal plates. Theinner, outer and bottom walls of the basket are made of perforated metalor chicken wire mesh (large openings of at least /2 inch). The lower 5and the upper 6 sections of the vertical cylinders are made of metalwhich is impervious to fluid flow.

Fabrics to be processed are placed inside the cylindrical spacedindicated by the number 7. Basket 2 is fastened at the bottom to acircular solid piece of metal 8 which is locked on a vertical shaft 9which is connected to a gearbox transmission device 10. The motion ofthe basket 2 is the result of rotational energy transmitted through asystem of shafts, belts and pulleys 9, 11, 12, 13 which are driven bymotor 14. The motor 14 is fastened at the bottom floor of the dryer andcontrols the rotational speed of the basket which contains the fabrics.The microwave energy system comprises a power supply, signal generator,con trol module 15 which is connected by a coaxial cable (not shown) tothe radiator 16 which contains a Klystron or Amplitron tube. This systememits electromagnetic energy to the contents of the basket. The mouth ofthe radiator is placed at the focus of a reflector 17 of paraboilc shapeWhich reflects the waves and transmits an upward microwave beam ofplane, coherent waves 18 having a plurality of parallel rays. Acircular, flat, Wave reflector 19 is fastened to the top of therevolving basket. This wave reflector can be easily removed at the endof a drying operation since it is fastened on its axis through a simplepressure arrangement 20 (swage lock). Continuous waves or pulsed Wavestrains 21 are reflected back downwards after they impinge against thebottom, lower side of the circular, flat reflector 19. A blower 22coupled to a motor (not shown) sucks in the outside air as shown by thearrows 23 after it passes through a filter (not shown). The air is blownin an upwards direction inside the dryer and follows the path indicatedby arrows 24. A circular space of the order of one or two inches heightis provided between the wave reflector 19 and the separation plate 25 toallow free escape of the moist air from the processing air. A circularpipe 26 fastened on the left wall above the level of the hinges 27conveys the wet air to a suitable home exhaust system (for instance, aflexible pipe connected with the outside). The bottom reflector(parabolic shape) 17 is supported by three legs 28 (each leg space at anangle of from the next). One of the legs 28 can be collapsed through ahinge system 29 for easy removal of the reflector 17.

The upper separation plate 25 supports a timer 30 which is of a typewhich is well-known in the art. To enable smoother rotation of thebasket 2, roller bearing units 31 of suitable lengths are in contactwith the upper section 6 and the lower section 5 of the basket.

A lid 32, which is mounted to hinges 33, is opened to load fabricsinside the dryer. It closes through a pressure switch arrangement 34 inthe front of the unit. A strip of rubber, plastic or other suitablematerial 35 issued to seal the dryer, when in operation, to make itradiation, leak proof. An access door 36, which is connected to twohinges 27, is located on the rear side of the unit to permit quickopening for servicing.

The electrical system which will enable complete automatic control ofthe drying-sterilizing operations is well within todays state of theart. For this reason electrical or electronic devices or components havebeen eliminated from FIG. 1 for the sake of simplicity. However, thepressure sensitive switches 37 and 38, which will shut off the maincircuit (and thus cut off microwave emission) when the user opens eitherthe top lid 32 or the rear access door 36, are shown. Also shown are thefront panel switches (push button type) which actviate the mainelectrical components of the apparatus: general switch, motor (basket),blower motor, microwave generator, timer, relay boxes etc. The main lineplug-in unit 40 is seen at the bottom of the rear side panel.

Lower separation plate 41 supports the microwave power supply, signalgenerator, control module 15. Support 42 is welded or otherwise suitablyaffixed to the lower side of the plate 41 to hold the rotating shaft 11,which transmits motion tothe gearbox 10, in line. A circular metal plate43 is attached to the main separation plate 41 by means of three legs 49which are best seen in FIG. 3. Gearbox and radiator 16 are fastened tothe center plate 43 by means of three short metal rods 44. The upperback panel, removable, plate'45 gives access to the electronic circuitryand wiring of the front panel.

FIG. 2 shows the shape of the upper separation plate 25 which issupported laterally by two right angle metal bars 46 welded to the sidewalls of the dryer. The dashed line yy is a projection of the axisaround which the upper lid 32 rotates. The outside wall 6 of the basketand the empty space 7 into which material to be irradiated is placed,may be seen in FIG. 2. The upper separation plate 25 supports a relaybox 47 and an automatic, electrically driven, timer 30. Also shown, indotted lines, is the projection of the cylindrical pipe 26 which is usedto evacuate moist air above the separation plate. Fastened to the bottomof plate 25 is pressure sensitive switch 38 which is also shown indotted lines. Pressure switch 38 cuts off the main line current as soonas someone opens the rear door for servicing. The roller bearings 31which help the basket to rotate smoothly are located at three positions(120 apart). They can be placed at different locations, if desired, orcompletely around the rotating path.

FIG. 3 is a cross sectional view at the level of the lower separationplate. Here again, it can be seen that the plate is supported laterallyand underneath by two right angle bars 48. Three heavy metal legs 49fasten the center plate 43 to the lower separation plate 41. Plate 41 isthicker than the upper plate 25 because it supports the heaviercomponents of the dryer. The numeral designates the space occupied bythe power supply, signal generator and control module which feeds themicrowave radiator through a standard, coaxial, insulated cable which isnot shown in the drawings. Also shown in dotted lines is the positionoccupied at a lower level by the shaft 11, the pulley, and the shaftsupport 42 which is fastened to the lower side of the plate 41.

FIG. 4 is a perspective view of the dryer-sterilizer seen from thefront. The front panel is provided with the different push-buttons whichsuccessively activate the main line switch 39, the blower 50, the basketmotor 51, the microwave signal generator 52, the timer 53, which can 6be set for various kinds of fabrics, and the general safety switch 54for immediate shut-off in case of malfunctioning or emergency. Apilot-light 55, when lit, indicates that the dryer is in operation. Theelectrical and/ or electronic circuitry, which enables one to performthe sequence of automatic operations hereabove mentioned, is well knownto anyone skilled in the art and for the sake of simplicity they are notdescribed in detail. Also shown in FIG. 4 is a disposable andreplaceable air filter 56 which can easily be fastened or removed fromthe external lower left side of the apparatus. The electrical connection40 with the main AC line or 220 volts, 60 cycles) is shown in the lowerrear side of the dryer. Also shown are optional roller casters 57 which,if needed, would help to easily move the unit to different locations inthe home.

FIG. 5 is the upper part of the unit represented in FIG. 4 but the lid32 has been opened to show the respective positions of the wavereflector plate 19, the safety switch 37 and the radiation insulatingjoint 35.

Without departing from the framework of the present invention it must bewell understood that, according to the results derived, the presentinvention can be applied to variable volumes of gas at differenttemperatures or at multiple pressures, and that, still without departingfrom the scope of the invention, the structural details of the describedapparatus, the dimensions and the shapes of their members (such as thebasket shape which could for instance be cylindrical with a plain solidrod on its axis) and their arrangement (the relative position of thebasket motor and blower for instance) may be modified, and that certainmembers may be replaced by other equivalent means (parabolic reflectorby a conical or ellipsoidal refiector).

In order to illustrate the possibilities of the invention moreconcretely, by a precise example, but without limiting the scope of theinvention, following is an example of a drying-sterilizing operation.With a dryer-sterilizer of the type hereabove described 7 pounds of wetlinen have been processed at an irradiation time between two and fiveminutes. The linen had a water content of the order of between 4 and 6'pounds. The microwave power output from the signal generator-radiatorsystem averaged between 0.5 and 1.5 kw. (continuous wave). The nominalemission frequency was 2450 MHz.:L25 MHz. The rotational speed of thebasket containing the wet linen was 10 revolutions per minute. Theblower capacity under loading conditions was of the order between 50 and100 standard cubic feet per minute. Hundreds of samples were taken aftereach drying operation for examination of the bacteriological flora. Alltests and bacteriological assays showed complete absence of livehousehold germs or viruses within the limit of the operating conditions.

The teachings of the invention may be practiced within the followingparameters:

Microwave energency frequency: 100 to 300,000 MHz.

Type of wave: continuous or pulsed at a repetition rate between one pernanosecond and one per minute Airflow: 10 to standard cubic feet perminute Basket rotation: 1 to 500 revolutions per minute Direction of themicrowave energy beam is parallel to the direction of airflow andtransverse to the direction of basket rotation.

While the invention has been described by means of specific examples andin a specific embodiment, it is not limited thereto, for obviousmodifications will occur to those skilled in the art without departingfrom the spirit or scope of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. The method of drying and sterilizing materials such as textiles whichcomprises:

placing the material in a metal container rotatable about a verticalaxis;

applying an electromagnetic field at a frequency in the 7 range of about100 to 300,000 MHZ. to the material;

moving a gas stream rapidly through the material;

the directions of the beam of the electromagnetic field and of the gasstream being parallel to each other and to the axis of rotation; and

rotating the material at a velocity of the order of between 1 and 500revolutions per minute.

2. The invention of claim 1 wherein the velocity of the gas stream is ofthe order of between 100 and 500 feet per minute.

3. The invention of claim 2 wherein the electromagnetic field is acontinuous wave emission. 4. The invention of claim 2 wherein theelectromagnetic field is a pulsed wave emission having a repetition rateof the order of between one per nanosecond and one per minute.

5. The invention of claim 1 wherein the electromagnetic field is acontinuous wave emission.

6. The invention of claim 1 wherein the electromagnetic field is apulsed wave emission having a repetition rate of the order of betweenone per nanosecond and one per minute.

7. The invention of claim 1 wherein at least a portion of the energy ofthe electromagnetic field is reflected through the material at leastonce.

8. The invention of claim 7 wherein at least a portion of the reflectedportion of the energy of the electromagnetic field is rereflectedthrough the material at least once. 9. The invention of claim 1 whereinthe velocity of the gas stream is of the order of between 100' and 500feet per minute and at least a portion of the energy of theelectromagnetic field is reflected through the material at least once.

10. The invention of claim 9 wherein at least a portion of the reflectedportion of the energy of the electromagnetic field is rereflectedthrough the material at least once.

11. Apparatus for drying and sterilizing materials comprising:

a metal basket for receiving the material to be dried which is rotatableabout a vertical axis thereof;

means for emitting a beam of electromagnetic energy through the materialparallel to the vertical axis of the metal basket;

means for moving a gas stream through the material in a directionparallel to the direction of the beam of electromagnetic energy;

means for rotating the metal basket such that the material containedtherein is subjected to the effect of the i beam of electromagneticenergy and the flow of gas stream.

12. The invention of claim 11 wherein:

the means for emitting a beam of electromagnetic energy through thematerial comprises:

a source of continuous waves and a reflector;

the reflector being spaced from one end of the basket and'rnounted sothat the electromagnetic energy is directed through the material inparallel rays.

13. The invention of claim v12 including a second reflector spaced fromthe other end of as basket so that at least a portion of theelectromagnetic energy is redirected through the material.

14. The invention of claim 11 wherein:

the means for emitting a beam of electromagnetic energy through thematerial comprises:

a source of pulse waves and a reflector;

the reflector being spaced from one end of the basket and mounted sothat the electromagnetic energy is directed through the material inparallel rays.

15. The invention of claim 14 including a second refiector spaced fromthe other end of the basket so that at least a portion of theelectromagnetic energy is redirected through the material.

16. Apparatus for drying and sterilizing materials such as textilescomprises:

a housing;

a cylindrical, metal drum to receive the materials trnounted within thehousing so as to be rotatable about a vertical axis with respectthereto;

means for emitting a beam of electromagnetic energy through the materialparallel to the vertical axis;

means spaced from one end of the drum for reflecting the beam ofelectromagnetic energy to produce a plurality of parallel rays;

means spaced from the other end of the drum for rereflecting the beam ofelectromagnetic energy;

means for moving a gas stream through the material in a directionparallel to the direction of propagation of the beam of electromagneticenergy;

means for rotating the drum in a direction transverse to the directionsof propagation of the beam of electromagnetic energy and of the movementof the gas stream;

at least a portion of the wall of the drum being perforated to permitthe free flow of the gas therethrough.

References Cited UNITED STATES PATENTS 6/1950 Frye 341 10/1966 Niebuhret a1 2l9l0.55

